Set dart runtime version with parsed `Platform.version` #958

Job	Run time
android \| ubuntu-latest \| stable	1m 6s
cancel-previous-workflow	3s
android \| ubuntu-latest \| beta	1m 6s
linux \| ubuntu-latest \| stable	2m 37s
linux \| ubuntu-latest \| beta	1m 16s
ios \| macos-latest \| stable	1m 3s
macos \| macos-latest \| stable	1m 2s
windows \| windows-latest \| stable	3m 31s
analyze / analyze	1m 19s
analyze / cancel-previous-workflow	16s
analyze / package-analysis	1m 37s
	14m 56s

Provide feedback